Mass transfer in SiO2 nanofluids: A case against purported nanoparticle convection effects

Controversy and the ambiguity exist in the scientific literature for the question of if nanoparticles truly enhance heat and mass transfer. This study experimentally explored effects of non-aggregating spherical SiO2 nanoparticles on oxygen and NaCl mass transfer. No mass transfer enhancements were found in the presence of nanoparticles. Oxygen transfer was actually diminished at the highest nanoparticle volume fraction; this is attributed to solution viscosity effects and the obstruction effects of impermeable nanoparticles. No evidence was found to substantiate the purported Brownian motion micro/nano-scale convection effect of nanoparticles that has been used by others to explain anomalous heat and mass transfer rates in nanofluids. (C) 2012 Elsevier Ltd. All rights reserved.